Drinking by portacaval shunted rats to regulatory challenges

Male rats received an experimental portacaval shunt (PCS) which diverted all of the hepatic-portal blood from the liver into the vena cava. Several months postsurgery, the regulation of fluid balance was evaluated in PCS and sham operated rats. PCS and Sham groups exhibited increased drinking in response to water deprivation and to an osmotic load, however, in both situations the PCS rats drank more than their surgical controls. Despite this difference in intake (adjusted for differences in body weight), the initial bout parameters of the PCS group following osmotic challenge were not appreciably different from those of the Sham group. The reduction of plasma volume with polyethylene glycol treatment elicited drinking in both PCS and Sham groups, with the former group consuming more fluid than the latter after polyethylene glycol but not after vehicle treatment. The results indicate that even after portacaval anastomosis rats were capable of increasing drinking in response to regulatory challenges and that the greater spontaneous fluid intake of PCS rats relative to controls which has often been observed persists during such compensatory responses.